update borgmatic config to backup btrfs subvolume

nixos/modules/backups.nix

@@ -1,39 +1,28 @@
 { pkgs, lib, config, ... }:
 let
   cfg = config.lab.backups;
-  snapshotFile = "/tmp/snapshot.qcow2";
-  snapshotMount = "/tmp/snapshot";
   beforeEverything = pkgs.writeShellScriptBin "beforeEverything" ''
-    ${pkgs.libvirt}/bin/virsh snapshot-create-as --domain ${cfg.domainName} --name backup-${cfg.domainName} --disk-only --quiesce --no-metadata --diskspec vda,snapshot=no --diskspec vdb,file=${snapshotFile} && ${pkgs.coreutils}/bin/sleep 1
-    ${pkgs.coreutils}/bin/mkdir -p ${snapshotMount}
-    ${pkgs.libguestfs-with-appliance}/bin/guestmount -a ${snapshotFile} -m /dev/sda1 --ro ${snapshotMount}
-  '';
+    if [ -d "${cfg.snapshotLocation}" ]; then
+      ${pkgs.btrfs-progs}/bin/btrfs subvolume delete ${cfg.snapshotLocation}
+    fi
 
-  afterEverything = pkgs.writeShellScriptBin "afterEverything" ''
-    set +e
-    ${pkgs.coreutils}/bin/sleep 10
-    ${pkgs.libguestfs-with-appliance}/bin/guestunmount ${snapshotMount} && ${pkgs.coreutils}/bin/sleep 1
-    ${pkgs.coreutils}/bin/rm -rf ${snapshotMount}
-    ${pkgs.libvirt}/bin/virsh blockcommit ${cfg.domainName} vdb --active --verbose --pivot
-    ${pkgs.coreutils}/bin/rm -f ${snapshotFile}
+    ${pkgs.btrfs-progs}/bin/btrfs subvolume snapshot -r ${cfg.subvolumeLocation} ${cfg.snapshotLocation}
   '';
 
   borgmaticConfig = pkgs.writeTextFile {
     name = "borgmatic-config";
     text = ''
       source_directories:
-      - ${snapshotMount}
+      - ${cfg.snapshotLocation}
       repositories:
       - path: ${cfg.repoLocation}
-        label: ${cfg.domainName}
+        label: nfs
       keep_daily: 7
       keep_weekly: 4
       keep_monthly: 6
       unknown_unencrypted_repo_access_is_ok: true
       before_everything:
       - ${beforeEverything}/bin/beforeEverything
-      after_everything:
-      - ${afterEverything}/bin/afterEverything
     '';
   };
 in
@@ -48,33 +37,44 @@ in
     };
 
     repoLocation = lib.mkOption {
-      default = "${config.lab.dataDisk.mountPoint}/backups/thecloud-data.borg";
+      # TODO: maybe make sure data disk is enabled? is there an "ensure" method in nix?
+      default = "${config.lab.dataDisk.mountPoint}/backups/nfs.borg";
       type = lib.types.str;
       description = ''
         Location of the Borg repository to back up to.
       '';
     };
 
-    domainName = lib.mkOption {
-      default = "thecloud";
+    subvolumeLocation = lib.mkOption {
+      default = "${config.lab.dataDisk.mountPoint}/nfs";
       type = lib.types.str;
       description = ''
-        The name of the Libvirt domain with the data disk attached.
+        Location of the btrfs subvolume holding the data.
+      '';
+    };
+
+    snapshotLocation = lib.mkOption {
+      default = "${config.lab.dataDisk.mountPoint}/nfs-backup";
+      type = lib.types.str;
+      description = ''
+        Location to (temporary) create a snapshot of the subvolume.
       '';
     };
   };
 
   config = lib.mkIf cfg.enable {
-    environment.systemPackages = with pkgs; [ libguestfs-with-appliance borgbackup ];
+    environment.systemPackages = with pkgs; [ borgbackup ];
     # Converted from:
     # https://github.com/borgmatic-collective/borgmatic/tree/84823dfb912db650936e3492f6ead7e0e0d32a0f/sample/systemd
     systemd.services.borgmatic = {
       description = "borgmatic backup";
       wants = [ "network-online.target" ];
       after = [ "network-online.target" ];
+
       unitConfig = {
         ConditionACPower = true;
       };
+
       serviceConfig = {
         Type = "oneshot";
         Nice = 19;
@@ -85,22 +85,19 @@ in
         Restart = "no";
         LogRateLimitIntervalSec = 0;
       };
+
       preStart = "${pkgs.coreutils}/bin/sleep 1m";
-      script = "${pkgs.systemd}/bin/systemd-inhibit --who=\"borgmatic\" --what=\"sleep:shutdown\" --why=\"Prevent interrupting scheduled backup\" ${pkgs.borgmatic}/bin/borgmatic --verbosity -2 --syslog-verbosity 1";
+      script = "${pkgs.systemd}/bin/systemd-inhibit --who=\"borgmatic\" --what=\"sleep:shutdown\" --why=\"Prevent interrupting scheduled backup\" ${pkgs.borgmatic}/bin/borgmatic --verbosity -2 --syslog-verbosity 1 -c ${borgmaticConfig}";
     };
 
-    environment.etc."borgmatic/config.yaml" = {
-      source = borgmaticConfig;
+    systemd.timers.borgmatic = {
+      description = "Run borgmatic backup";
+      wantedBy = [ "timers.target" ];
+      timerConfig = {
+        OnCalendar = "*-*-* 3:00:00";
+        Persistent = true;
+        RandomizedDelaySec = "3h";
+      };
     };
-
-    # systemd.timers.borgmatic = {
-    #   description = "Run borgmatic backup";
-    #   wantedBy = [ "timers.target" ];
-    #   timerConfig = {
-    #     OnCalendar = "*-*-* 3:00:00";
-    #     Persistent = true;
-    #     RandomizedDelaySec = "3h";
-    #   };
-    # };
   };
 }